1. Field of the Invention
The present invention relates to a complex wireless service apparatus using wired and wireless communication systems and a method thereof wherein when a call of a complex wireless terminal is not reachable, a call forwarding is automatically tried through another network by making a position of a service user to be registered automatically using the complex wireless terminal, and the service user can make a speech without any disconnection using a hand off between networks for the complex wireless terminal when the user moves from one network to another network during making a call.
2. Description of the Related Art
The most common communication for the general public can be called a general wired telephone using a public telephone network.
Additionally, home communication equipment whose mobile usage is restricted to a user's residence started to appear in Korea from the end of 1970's, which is so-called a cordless phone.
This cordless phone has a usage frequency of 46/49 Mhz (megahertz), a common indoor reachable distance of about 50 m (meters), a channel gap of 25 Khz (kilohertz) and an FM (Frequency-Modulation) modulation scheme. It commonly uses an MCA (Multi Channel Access) scheme which can be called a request channel scheme from the middle of 1980's even though a fixed channel scheme was adopted in the earlier time.
A cordless phone of 900 Mhz bandwidth appeared taking an enhance of speech quality into account from the early 1990's.
The cordless phone which is modified to be used only in the residence by making the general phone operable in the wireless environment is called CT-1 (First Generation Cordless Phone).
The CT-1 cannot be used in a public place since it was devised for home usage. In order to improve such a problem, an originating dedicated mobile phone, so called CT-2 (Second Generation Cordless Phone) system was suggested for the first time in the United Kingdom in 1989 and adopted as a European standard in Europe. The CT-2 system is currently serviced in several countries and was serviced as a commercial service in Korea in the early 1997.
To directly express the property of the CT-2, it can be called a wireless public telephone for a pedestrian, which is used as the CT-1 at home and is used as a public phone in a public place which enables the user to make a speech within 200 m from the public telephone on walking.
A defect of the CT-2 is that there are no functions of call forwarding and handover. A CT-3 (Third Generation cordless Phone) appeared to supplement such a defect.
The CT-3 can be stated by classifying it into private and public network dimensions in accordance with its use, which can be explained centering around a PBX (Private Branch exchange) system in the private network dimension.
A communication system used for business in the existing building generally uses the PBX system and a system capable of mobile communication in a building by making the PBX system operable in a wireless environment is a wireless PBX which corresponds to many systems including a DECT (Digital European Cordless Telephone).
The DECT system regarded as a representative of the CT-3 was adopted as a European standard by ETSI (European Telecommunications Standards Institute) on March, 1992.
The main properties of this system are that its wireless connection is performed in a TDMA (Time-Division Multiple Access) scheme, its bandwidth is 2 Ghz (gigahertz), and a channel bandwidth is 1.73 Mhz so that each channel has 12 slots.
On developing the CT-3 system into a public network dimension by supplementing the system functions such as a handover and a roaming, a Low Tier PCS (Personal Communication Service) appeared, which is a personal communication realizing a personal communication enabling a user to make a speech regardless of whenever, wherever and with whomever and being evolved from the cordless phone.
The Low Tier PCS (Personal Communication Service) is a scheme by which pedestrian and indoor services can be provided on the basis of the cordless phone, such as DECT in Europe, PHS (Personal Hand-phone System) in Japan and PACS (Personal Access Communication Service) in the United States.
On the other hand, there is a High Tier PCS (Personal Communication Service) corresponding to the Low Tier PCS (Personal Communication Service), which becomes a micro cell developed from analog cellular technology in order to provide a service centered around a vehicle including a pedestrian.
The analog cellular which becomes a basis of the High Tier PCS (Personal Communication Service) was developed by AMPS (Advanced Mobile Phone Service) on October, 1983 with the aid of Bell Lab., one of its property is that it introduced a cell concept wherein its channel bandwidth is 30 kHz in 824 to 894 MHz and its modulation scheme is FM.
A system of the analog cellular mode is used as NMT (Nordic Mobile Telephone) and TACS (Total Access Cellular System) in Europe and as NTT method in Japan.
However, as such systems experience the capacity limitation as mobile communication subscribers are abruptly increased in the end of 1980, communication quality reduction due to the increase, and various requests for service, a method appears to improve the problems.
In order to improve the defects of the analog cellular such as a low capacity, low communication quality and limited data services, Korea developed narrowband CDMA (Code-Division Multiple Access) scheme and made a commercial service from early 1996, and United States standardized IS-95 CDMA on July, 1993 and also developed IS-54 TDMA scheme.
Also, GSM (Group Special Mobile) scheme first started in Europe in the end of 1992, which commercially used the TDMA in a pan-European style and had a property that it can be connected to each nation of Europe.
Japan commercialized a PDC (Public Digital Communication) scheme using the TDMA in early 1993.
However, such a digital cellular system does not seem to be a reasonable price for the public to have even though it seems to solve a quality of speech and a capacity to some degree. That is, the system does not seem to be improper for providing a general service.
Accordingly, the High Tier PCS (Personal Communication Service) seems to be evolved to make the digital vehicle mobile phone system to be generalized service and has merits that it provides high speed mobility and simple network construction, and can utilize the digital cellular technology.
The High Tier PCS (Personal Communication Service) system includes an Up-band IS-95 CDMA scheme evolved from the IS-95 CDMA and a DSC-1800 (Digital Communication System) scheme evolved from the GSM.
Though the development of PCS (Personal Communication Service) system can be divided into the High Tier PCS (Personal Communication Service) and Low Tier PCS (Personal Communication Service) as stated above, the High Tier scheme is recently being modified to accept the Low Tier scheme, and vice versa, so that the schemes are on a trend that they are integrated into an IMT-2000 (FPLMTS, Future Public Land Mobile Telecommunication System).
A communication network of the IMT-2000 is a network integrating wired and wireless communication services to be interconnected mutually, wherein many experts expect that an activation of a wireless Internet having the same transmission speed as that of a wired Internet can be visualized by constructing a network which can provide a low speed data transmission (14.4 kbps (kilobits per second)) being a wireless environment and a high speed data transmission (384 kbps).
Recently, various wired and wireless integration systems are being developed, which enable the wired and wireless integration service to be performed by integrating a wired network such as a public phone network and a wireless network such as a mobile communication network which have been already constructed as a post-stage of the IMT-2000.
Also, a mobile terminal (hereinafter, referred as a complex wireless terminal since it provides a plural band service and a plural mode service with a mobile terminal) supporting the plural band and plural mode is under the development in view of the mobile terminal. For example, there is a mobile terminal having dual band/dual mode which can provide a function of the mobile phone and a function of the mobile communication simultaneously.
The mobile terminal of the dual band/dual mode simultaneously providing the functions of wireless phone and mobile communication is called a dual bandwidth terminal since it can support both a frequency band used in wireless phone and a frequency band used in a mobile communication, and a dual mode terminal since it can support both a wireless phone mode and a mobile communication mode.
Besides them, there are a PCS/AMPS typed mobile terminal as the dual mode mobile terminal and a GSM900/GSM1800 as the dual band mobile terminal.
Such a plural band/plural mode mobile terminal can be operated in both single band/single mode and dual band/dual mode by a user's manual operation. Of course, it is possible to maintain a connection to a communication network which can guarantee a higher quality of speech in the case that there is transferred from a communication network to another communication network automatically.
Recently, there has been remarkably developed technology related to a wireless communication network and suggested many technology standards. Among them, Bluetooth technology standard and wireless LAN (Local Area Network) field are technology standards being spotlighted, which are closely related with the mobile terminal and produce a development of the mobile terminal of the plural band/plural mode.
However, a conventional method using the complex wireless terminal having the plural band/plural mode has a problem that when a network failed to receive a call a receiver has to retry a call establishment to another network since the networks were separated.
Therefore, services in a shadowed area, a basement and in-house are sometimes deteriorated in the cases of CDMA, GSM and WCDMA (Wideband Code Division Multiple Access) which provide broadband service areas so that repeaters should be installed for those places with separate expenses.
Though the communication systems such as WLAN and BLUETOOTH providing services in narrow areas can provide a good quality of services with low expenses, their service areas are not wide and their mobility is limited so that it is necessary to develop technology for enlargement of service area and guarantee of mobility.
Also, there is a problem that when a user of the complex wireless terminal having the plural band/plural mode moves from a general public phone network to a mobile communication network during making a call, or from the mobile communication network to the general public phone network, a speech is disconnected since a handoff is not provided between the two networks.